I spent all day Saturday swapping my 85 timing cover, front counterweight, oil pump, flywheel, and oil pan on to my RX2's early 12A so I could put it in my RX7, only to find out the tranny bolt pattern is different.

Now for the question.

Does anyone know if the tension bolts are the same betwen a 73 12A and the later ones? I didn't take the flywheel back off to check. If I can swap rear housings, I'll break the motor the rest of the way down and cut a bridgeport on the center and end housings My carb is gonna be too small then though. Oh well, I just want my damn car back on the road. This has been the longest "clutch" job I've ever had

 

Felix, have you checked out Felix Miata's web page?

Better yet, I have a '73 RX-2 12A and an '83 RX-7 12A. Both have been torn down. Everything about those engines is different. From the exhaust manifold bolt pattern, to the location of the alphanumeric "12A" on the rotor housing.

Believe me, I spent a long time trying to figure out the ins and outs of twin dizzy vs '74 and later engines. You wanna know what I came up with? 13B!!! Yep, I installed a 13B where an old RX-2 12A used to be. It involved shortening the driveshaft by 60mm (if I remember correctly) and moving the shifter boot back a bit, as well as a few other odds -n- ends.

So for you, it would be best to bridge port your RX-2 engine and stick it back in your RX-2. I wouldn't recommend installing the 2's 4 speed tranny in your 7.

Oh, and I think the tension bolts are different too (gotta compare them).

 

I figured if anyone would know, it would be you.

The RX-2 motor is already streetported, I think I'll just put it back in with the single dizzy and get another 12A single dizzy cover for the 7. My 85 12A is still in decent shape, just low, low compression. I have a couple dead 13B 6 port engines (and some turbo rotor housings) I could probably use with the 85 12A irons to make my own 4 port 13B (if thats possible). Then bridgeport that I guess my car is going to be off the road all damn winter

 

Probably untill next spring by the info you shared. Well, the RX-2 engine should be good for a while longer, hopefully.

Yeah, go ahead and get another single dizzy front cover for your other engine so you can use electronic dizzys in both engines (then you know what comes next ).

Check out these pics of the tranny in my MG. Try to guess which one bolted to the RX-2 engine.
http://www.geocities.com/cd23c/cars.html#mg

Do an ATF treatment on your RX-7 engine to try to bring the compression up a bit by loosening the carbon in the apex slots on the rotors. If anything will help aside from new seals and springs, its the ATF. Try it with ATF, then MMO on seperate occasions just to satisfy the old corn rustlers here

You won't be able to mix '86 and later 13B parts with '85 and older parts because the O rings were moved from the rotor housings to the cast iron housings (dumb move on Mazda's part, unless they had an extremely good reason for it, which I doubt).

Hmm, maybe you could fill in the '85 rotor housings with devcon so the grooves are completly flatened and use them with the '86 and later cast irons. But don't try to mix '86 rotor housings with '85 iron housings because there is no groove in either one.

Just try to get your RX-2 going again, at least.

 

I did that already. Results: 25 psi rear, 65 front


One more thing, I put the 225mm clutch, flywheel, and front counterweight on. Will that clear the old 4 speed trans in the Rx-2, and will the old top mount starter still work?

 

Its gonna vibrate! Don't mix the later style flywheel with early rotors. The bolt pattern of the RX-2 bellhousing is different from the RX-7 bellhousing.

 

Dammit, I have to take that thing all the way back apart?

I wonder why Mazda quit using a tensioner on the oil pump chain....

 

damn, sure looks like alot of fun..... maybe the trans i have sitting in my garage will fit it...

 

Goddammit I wish I'd kept my GSL-SE now

I think I'll do some experimenting with the 6 port engines...